In general, an isobutylene-isoprene rubber has been used for an adhesive composition and an adhesive sheet due to excellent chemical resistance, excellent water vapor resistance, excellent electrical insulation properties, and the like, but has a problem in that it is difficult to cure the rubber because the rubber contains a small amount of unsaturated bonds.
In order to solve the problem, when the isobutylene-isoprene rubber is cured by carrying out a vulcanization treatment on the rubber, optical characteristics may deteriorate due to the occurrence of a discoloration phenomenon in which colors are changed, and the vulcanization treatment process essentially requires a high temperature process and thus has inferior workability and involves risks.
Further, when the isobutylene-isoprene rubber is cross-linked through halogen substitution, the isobutylene-isoprene rubber is harmful to the human body and may cause environmental pollution due to the toxicity of halogen elements.